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<h2><b>fndlvl()</b></h2>
<p>
<code>fndlvl (<i>expr, expr_to_find, lev1, lev2</i>)</code>
<p>
Given two gridded variables, <code><i>expr</i></code> and
<code><i>expr_to_find</i></code>, this function finds the first
vertical level at which the <code><i>expr_to_find</i></code> value
occurs in <code><i>expr</i></code>. <code><i>lev1</i></code> and 
<code><i>lev2</i></code> specify the range of
levels over which to search. The result is a grid of pressure values.

<p>
<h3>Usage Notes</h3>
<ol>
<li>The dimensions of <code><i>expr</i></code> and
<code><i>expr_to_find</i></code> &nbsp must match. 
</ol>

<p>
<h3>Examples </h3>
<p>
<ol>
<li>This example finds the pressure levels of the 240 degree isotherm:
<p>
<ul><code>d fndlvl (t, const(t,240), lev=1000, lev=100)</code></ul>
<p>
<li>The <code><i>expr_to_find</i></code> doesn't have to be a constant;
it can change with location. This example returns the pressure
level of the tropopause, given the variable <code>'ttrop'</code> that 
contains the temperature at the tropopause: 
<p>
<ul><code>d fndlvl (t, ttrop, lev=1000, lev=100)</code></ul>
<p>
<li>This example illustrates the limitations of
<code>fndlvl</code>. It returns the level of the surface pressure
variable <code>psfc</code> in the coordinate system of
<code>lev</code>, a GrADS <a href="variable.html">pre-defined variable</a>.
<p>
    <ul>
      <code>d fndlvl (lev, psfc, lev=1000, lev=100)</code> 
    </ul>
<p>
The display should be exactly the same as <code>psfc</code> except in 
locations where <code>psfc</code> is greater than 1000 mb, the maximum value of 
<code>lev<code>.
</code></code></ol>

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